Disks need more line pressure vs drums. A smaller diameter master helps. I understand a 15/16" master is about as small as you can go and still maintain adequate fluid volume. Dr Diff offers a 15/16" AL master with adapter. I run one on a PB setup.

As far as the prop valve, an adjustable valve on the rear line is best with a disc/drum setup. Wilwood or similar.

Will you like front discs on a "B" without power assist? Not so sure! It depends in part on the calipers and friction material. Stock calipers can have generous piston area and are probably best for this swap. Some aftermarket calipers have smaller piston area and really need the booster. Low cost organic pads also have more cold bite. Hi- po/high temp pads not so much and you may like the booster.